Quantity and quality of soil organic matter as a sustainability index under different land uses in Eastern Amazon

Diana Signor,Plínio Barbosa de Camargo,Carlos Eduardo Pellegrino Cerri,Magnus Dall’Igna Deon

doi:10.1590/1678-992x-2016-0089

Diana Signor, Plínio Barbosa de Camargo + Show 2 more

Open Access

https://doi.org/10.1590/1678-992x-2016-0089

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Abstract

Soil organic matter (SOM), which influences chemical, physical and biological soil attributes, is the main form of C found in the soil which can also be used as a soil sustainability index. The aim of this study was to use the quantity and quality of SOM as an indicator to determine the sustainability of different land uses (native vegetation, secondary vegetation, fruit orchards, horticultural areas, degraded pasture, improved pasture, and fields with annual crops) in the eastern Amazon. Improved pasture had higher soil C stock than the other land uses and was similar to the native vegetation, and also presented the highest quantity of C in a stable form in the soil (fraction < 53 im). According to the C management index, improved pasture is the most similar in use to native vegetation. Changes in land use reduced the soil microbial C content, although the more conservationist systems (fruit orchards, secondary vegetation, and improved pasture) had contents similar to those of the native vegetation. The highest soil microbial quotients were found in fruit orchards and horticultural areas. Well-managed pastures were effective in accumulating C as stable forms in the soil, which demonstrates the sustainability of this land use in the region studied.

Highlights

Soil organic matter (SOM), which influences chemical, physical and biological soil attributes, is the main form of C found in the soil which can be used as a soil sustainability index
The aim of this study was to use the quantity and quality of SOM as an indicator to determine the sustainability of different land uses in the eastern Amazon
Soil organic matter (SOM) is the main form of C found in the soil (Brady and Weil, 2008) and can influence chemical, physical and biological soil attributes, be a source of C and energy for microorganisms and affect greenhouse gas emissions (Batjes and Sombroek, 1997)

Summary

Introduction

Soil organic matter (SOM) is the main form of C found in the soil (Brady and Weil, 2008) and can influence chemical, physical and biological soil attributes, be a source of C and energy for microorganisms and affect greenhouse gas emissions (Batjes and Sombroek, 1997). In the Amazon in Brazil, deforestation makes way for the establishment of pastures and recently, grazing areas have been replaced by corn and soybean fields (Frazão et al, 2010; Lammel et al, 2015) This can reduce the C in the 0-20 cm soil layer by 10 %, while changing from agriculture to pasture the soil C content may increase by 26 % (Don, 2011), and achieve a level similar to the native areas (Frazão et al, 2010; Maia et al, 2009). SOM is an important indicator of soil quality and agricultural sustainability, since management practices can cause it to undergo rapid change (Mielnickuk, 2008) Such change can be evaluated using the total soil C content, its chemical and physical fractions or by a combination of these factors (Blair et al, 1997). Labile C, resulting from soil oxidation with K2Cr2O7 at different acidity levels or by physical fractionation of SOM, as well as the microbial biomass can be used as indicators of sustainability for agricultural systems (Araújo and Melo, 2010; Dieckow et al, 2005; Chan et al, 2001)

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